Single-dose syringe driver

ABSTRACT

Various methods and devices for driving fluid from a syringe are provided. In one exemplary embodiment, a luer fitting for connecting a syringe barrel to a syringe driver is provided that includes a proximal female end including a socket adapted to be removably mated to a male luer fitting on the syringe barrel. The luer fitting further includes a distal end including a nozzle adapted to receive a fluid conduit. The distal end has a non-threaded axially-oriented annular socket formed therein for removably receiving a protrusion on the syringe driver.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. application Ser. No.12/973,243, filed on Dec. 20, 2010, now U.S. Pat. No. 8,231,576, whichis a continuation of U.S. application Ser. No. 11/277,848 filed on Mar.29, 2006 and entitled “Single-Dose Syringe Driver,” now U.S. Pat. No.7,867,197, each of which are hereby incorporated by reference in theirentirety.

FIELD OF THE INVENTION

The present invention relates to devices and methods for driving fluidfrom a syringe.

BACKGROUND OF THE INVENTION

Certain medical fluids are administered by controlled infusion andrequire a slow but non-rate critical flow rate. Infusion of a medicalfluid in this manner has generally been accomplished by use of a dripbag gravity-feed system or an electronic infusion pump. The drip bagprovides a non-rate critical flow with a simple and relativelyinexpensive apparatus. However, in certain applications, particularlythose involving small fluid volumes, the use of disposable syringes ispreferred to drip bags. Administration of medical fluids at a low flowrate using a syringe is generally accomplished by the use of apredetermined force that is applied to the syringe plunger so that fluidresistance acts to control the flow rate. Current devices for applyingforce to a syringe plunger can have a housing for holding the syringeand a simple mechanism located within the housing that causes force tobe applied to the plunger. While effective, these devices are oftendesigned to be used with proprietary syringe sets, rendering medicalfluid administration expensive.

Accordingly, there remains a need for an improved syringe driver, and inparticular for a syringe driver that can be used with standard medicalsyringes.

SUMMARY OF THE INVENTION

A variety of techniques can be used to mate a syringe to the device, butin one exemplary embodiment the driver includes a cavity formed thereinand adapted to capture a flange formed on a proximal end of a plunger ofa syringe, and the frame includes a connecting element formed on adistal end thereof and adapted to connect to a distal end of a syringe.The connecting element can include, for example, a cavity that isadapted to receive a barrel of the syringe and a protrusion that isadapted to receive at least a portion of a detachable luer fitting formating to a distal end of the barrel of the syringe. The detachable luerfitting can be configured to mate to any standard syringe, therebyallowing the device to interchangeably receive syringes having varioussizes. In one embodiment, the luer fitting can have a non-threadedsocket formed therein for receiving the protrusion formed on theconnection element.

A variety of techniques can be used to mate a syringe to the device, butin one exemplary embodiment the driver includes a cavity formed thereinand adapted to capture a flange formed on a proximal end of a plunger ofa syringe, and the frame includes a connecting element formed on adistal end thereof and adapted to connect to a distal end of a syringe.The connecting element can include, for example, a cavity that isadapted to receive a barrel of the syringe and a protrusion that isadapted to receive at least a portion of a detachable luer fitting formating to a distal end of a barrel of a syringe. The detachable luerfitting can be configured to mate to any standard syringe, therebyallowing the device to interchangeably receive syringes having varioussizes. In one embodiment, the luer fitting can have a non-threadedsocket formed therein for receiving the protrusion formed on theconnection element.

The driver, puller, and force-delivery element can also have a varietyof configurations, and they can be coupled to the frame using a varietyof techniques. In one exemplary embodiment, the frame can include aproximal portion for slidably seating the driver therein, and a distalportion for slidably seating the puller. The frame can optionallyinclude rails formed thereon for slidably retaining the driver withinthe frame, and a housing that at least partially surrounds the puller toretain the puller within the frame. In certain exemplary embodiments,the force-delivery element can be adapted to force the puller intocontact with the housing to generate friction between the puller and thehousing when the puller is in the first position, and thereby helpretain the puller in the first position. The driver can also include afirst engagement surface formed thereon and adapted to act against asecond, complementary engagement surface formed on the puller to furtherforce the puller into contact with the housing to generate a frictionbetween the housing and the puller when the puller is in the firstposition. The engagement surfaces can be, for example, complementaryramp elements.

As indicated above, the puller is preferably adapted to mate to a distalend of the frame to actuate the force-delivery element, and thereby movethe driver to advance a plunger into a syringe held within the frame.While various techniques can be used to mate the puller to the distalend of the frame, in one embodiment the puller can include a latchformed on a distal end thereof, and the frame can include an engagementelement formed on a distal end thereof. The puller can optionallyinclude one or more handles formed thereon for slidably moving thepuller to mate the latch to the engagement element. The latch andengagement element can be releasably matable, and depression of thehandle(s) can be adapted to release the latch from the engagementelement.

A system for driving fluid is also provided and includes a syringehaving a barrel and a plunger slidably disposed in the barrel, and asyringe driver having a frame with a proximal end and a distal end thatis adapted to couple to a distal end of the barrel of the syringe. Adriver is slidably disposed within the frame and is adapted to retain aproximal end of the plunger. A puller is slidably disposed within theframe and is movable between a first position, in which the puller ispositioned adjacent to the driver, and a second position, in which thepuller is coupled to a distal end of the frame and a force is applied tothe driver to move the driver distally, and thereby force the plungerinto the barrel of the syringe. The syringe driver can also include aforce-delivery element extending between the puller and the driver. Theforce-delivery element can be in a resting position when the puller isin the first position, and the force-delivery element can be actuated toapply a force to the driver when the puller is in the second position.

In another embodiment, a system for driving fluid can include a syringehaving a barrel, a plunger slidably disposed in the barrel, and a luerfitting coupled to a distal end of the barrel for mating the barrel to afluid conduit. The system can also include a frame having proximal anddistal ends, the proximal end adapted to retain the plunger and thedistal end having a connecting element formed thereon adapted to coupleto the barrel of the syringe. The connecting element can include aprotrusion that is configured to extend into a non-threaded socketformed in the luer fitting to removably mate the barrel to the frame.

Methods for driving fluid are also provided. In one exemplaryembodiment, the method can include engaging a syringe between a driverslidably positioned within a frame and a connecting element formed on adistal end of the frame, and sliding a puller toward a distal end of theframe to mate the puller to the frame. Sliding the puller will actuate aforce-delivery element coupled to and extending between the puller andthe driver. Once actuated, the force-delivery element will move thedriver distally to drive a plunger into a barrel of the syringe andthereby drive fluid out of the syringe. In an exemplary embodiment, thepuller can be slid by sliding opposed handles formed on the pullerdistally within opposed slots formed in the housing. Depressing theopposed handles can be effective to release the puller from the frame.In another exemplary embodiment, engaging the syringe can includepositioning a flange formed on a proximal end of a plunger of thesyringe in a cavity formed in the driver, and positioning a luer fittingcoupled to a distal end of the syringe within a protrusion formed on theconnecting element.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more fully understood from the following detaileddescription taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 is a perspective view of one embodiment of a syringe and asyringe driver for driving fluid from a syringe;

FIG. 2A is a perspective view of a frame of the syringe driver of FIG.1;

FIG. 2B is a perspective view of the bottom portion of the frame of FIG.2A;

FIG. 2C is an enlarged perspective view of a connecting element forreceiving a syringe located on the distal end of the frame of FIG. 2A;

FIG. 3A is a top perspective view of a driver of the syringe driver ofFIG. 1;

FIG. 3B is a bottom perspective view of the driver of FIG. 3A;

FIG. 4 is a perspective view of a force-delivery element and the driverof FIG. 1;

FIG. 5A is a top perspective view of a puller of the syringe driver ofFIG. 1;

FIG. 5B is a bottom perspective view of the puller of FIG. 5A;

FIG. 5C is a perspective view of a latch on the distal end of the pullerof FIG. 5A;

FIG. 6 is a cross-sectional view of a proximal portion of the syringedriver of FIG. 1 taken across line A-A;

FIG. 7 is a partially exploded view of the syringe and a luer fitting ofthe system of FIG. 1;

FIG. 8A is a perspective view of the system of FIG. 1 in use, showingthe driver and the puller in an initial position;

FIG. 8B is a perspective view of the system of FIG. 8A, showing thepuller engaged with the distal portion of the frame;

FIG. 8C is a perspective view of the system of FIG. 8B, showing thedriver moved in a distal direction to advance a plunger into a barrel ofthe syringe;

FIG. 9A is a schematic of one embodiment of the system of FIG. 1 in use;

FIG. 9B is a schematic of an anti-siphoning feature of the system ofFIG. 1;

FIG. 9C is a schematic of another anti-siphoning feature of the systemof FIG. 1;

FIG. 9D is a schematic of another anti-siphoning feature of the systemof FIG. 1; and

FIG. 10 is a cross-section view of one exemplary luer fitting for usewith the system of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

Certain exemplary embodiments will now be described to provide anoverall understanding of the principles of the structure, function,manufacture, and use of the devices and methods disclosed herein. One ormore examples of these embodiments are illustrated in the accompanyingdrawings. Those of ordinary skill in the art will understand that thedevices and methods specifically described herein and illustrated in theaccompanying drawings are non-limiting exemplary embodiments and thatthe scope of the present invention is defined solely by the claims. Thefeatures illustrated or described in connection with one exemplaryembodiment may be combined with the features of other embodiments. Suchmodifications and variations are intended to be included within thescope of the present invention.

The present invention generally provides devices and methods for drivingfluid from a syringe. In general, the system includes a syringe that canbe mated to a syringe driver to cause fluid to be driven from thesyringe, preferably at a constant rate. FIG. 1 illustrates one exemplaryembodiment of a device for driving fluid from a syringe. As shown, thedevice 10 includes a frame 12 that is adapted to seat a syringe 60, adriver 30 slidably disposed within the frame 12 and adapted to apply adriving force to the syringe 60, and a puller 40 slidably disposedwithin the frame 12 and adapted to move the driver 30 relative to theframe 12. The device 10 can also include a force-delivery element (notshown) coupled to and extending between the driver 30 and the puller 40.In use, the puller 40 can be moved from an initial position to anactuated position to actuate the force delivery element. As a result,the force-delivery element will force the driver 30 distally to move aplunger 62 of the syringe 60 into a barrel 64 of the syringe 60, therebyforcing fluid out of the syringe 60. The system is particularlyeffective for delivering medical fluids such as antibiotics,chemotherapy agents, and other drugs typically handled in IV bags,however the syringe can be used to deliver any fluid.

FIGS. 2A-2C illustrate the frame 12 of the syringe driver 10 in moredetail. While the frame 12 can have any shape, size, and configuration,in the embodiment shown in FIG. 2A the frame 12 is in the form of asubstantially rectangular-shaped housing with proximal and distal ends12 a, 12 b. The frame 12 can have a unitary configuration, or it caninclude a top and bottom portion 14, 16 that mate together. A two-piececonfiguration is advantageous as the top and bottom portions 14, 16 canseat the driver 30, puller 40, and force-delivery element therebetween,and the top portion 14 can be adapted to hold the syringe. The frame 12can also optionally include features to facilitate grasping of thepuller 40 and use of the device 10. As shown in FIG. 2A, the frame 12includes two protrusions 26 a, 26 b formed on opposed sidewalls thereofto receive the thumbs of a user to facilitate movement of the puller 40,as will be discussed in more detail below. The frame 12 can also includemounting features integrally formed thereon or coupled thereto thatallow the device 10 to be hung from a rack or mounted to a vertical orhorizontal surface depending upon the needs of the user. Exemplarymounting features include, for example, hooks, one or more bores orscrew holes for receiving a fastener, adhesive, etc.

As noted above, the driver 30 and the puller 40 can be slidably disposedwithin the frame 12. While various techniques can be used to slidablycouple the driver 30 and the puller 40 to the frame 12, in theembodiment shown in FIG. 2B the bottom portion 16 of the frame 12includes a first set of tracks or rails 20 a, 20 b formed on a bottomwall thereof for seating the driver 30, and a second set of tracks orrails 22 a, 22 b formed on opposed sidewalls thereof for seating thepuller 40. The frame 12 can also include features that allow a user toslide the puller 40 within the tracks 22 a, 22 b such that the puller 40can be moved from a first position to a second position to causemovement of the force-delivery element. For example, referring back toFIG. 2A, the top and bottom portions 14, 16 of the frame 12 can includeslots 24 a, 24 b that are adapted to receive handles 44 a, 44 b locatedon the puller 40. Movement of the handles 44 a, 44 b within the slots 24a, 24 b can actuate the puller 40 to thereby actuate the force-deliveryelement, as will be discussed below.

The top portion 14 of the frame 12 can be adapted to receive a syringe.While the frame 12 can have various features for seating a syringe, FIG.2A illustrates a semi-cylindrical cavity 17 formed thereon for seating abarrel of the syringe. A plunger on the syringe can couple to the driver30, as will be discussed below, and a distal end of the syringe cancouple to the frame 12. While various mating techniques can be used, inan exemplary embodiment the top portion 14 of the frame 12 includes aconnecting element formed thereon having a cavity 28 for seating aconnector that couples to a distal end of the syringe to hold andsupport the syringe within the cavity 17 of the frame 12. The cavity 28can have any shape and size, and the configuration of the cavity 28 canvary depending upon the connector used. However, in an exemplaryembodiment the connector is in the form of a luer fitting that can beused with any size syringe, and the cavity 28 is in the form of asemi-circle with proximal and distal ends 28 a, 28 b. An exemplary luerfitting will be discussed in more detail below with respect to FIGS. 7and 10. The connecting element can also include features to preventinadvertent engagement with the wrong type of fitting, such as roundedcorners 27. In an exemplary embodiment, the distal end 28 b of thecavity 28 includes a protrusion 29 extending therefrom and adapted toextend into and mate with the luer fitting. The protrusion 29 can havevarious shapes and sizes. As shown in FIG. 2C, the protrusion 29 issemi-circular. The protrusion 29 can also include features, such as acut-out 31, for seating a fluid conduit, such as tubing, for carryingfluid that extends from the luer fitting. The connecting element can beformed integrally with the frame 12 or separate therefrom. In oneembodiment, the connecting element is separate from the frame 12 and canbe slid into a slot (not shown) located on the distal end 14 b of thetop portion 14. This allows the connecting element to be replaced shouldthe protrusion 29 break as a result of stress from the weight of thesyringe.

A person skilled in the art will appreciate that the frame 12 can have avariety of other configurations and it can include a variety of otherfeatures known in the art. For example, as shown in FIG. 2A, the topportion 14 can include a cut-out 11 formed therein for receiving thedriver 30 therethrough. As a result, the top portion 14 can include aflange 13 that can be located around the cut-out 11 to retain the driver30 and the puller 40 within the frame 12.

The driver 30 is shown in more detail in FIGS. 3A-4, and while it canhave a variety of shapes and sizes, in an exemplary embodiment thedriver 30 is in the form of a housing that is adapted to hold aforce-delivery element, as will be discussed below. As previouslydiscussed, the driver 30 can be slidably disposed within the frame 12.To facilitate sliding, the driver 30 can include wheels 32 a, 32 b, 32c, 32 d that are located on opposed sides of the housing and that areadapted to sit within the tracks 20 a, 20 b in the bottom wall of theframe 12 (shown in FIG. 2B). The driver 30 can also be adapted to seat aportion of the syringe, and thus the distal end 30 b of the driver 30can include a cavity 34 or other feature formed therein for receivingthe plunger of a syringe or other device for advancing a plunger into asyringe. While the cavity 34 can merely be molded within the driver 30,it can alternatively be adapted to facilitate engagement with theplunger. For example, the driver 30 can include a latch 36 formedthereon and configured to engage a flange formed on the proximal end ofthe plunger of the syringe. The driver 30 can also include aspring-loaded backwall (spring 39 is shown in FIG. 6) to facilitateinsertion and removal of the plunger from the cavity 34. In use, whenthe syringe is coupled to the driver 30, the driver 30 can slide withinthe cut-out 11 of the frame 12 to cause the plunger to be driven intothe barrel of the syringe.

As previously indicated, the device 10 can also include a force-deliveryelement coupled between the driver 30 and the puller 40 that can be usedto apply a force to the driver 30 to cause the driver 30 to drive aplunger into a barrel of a syringe seated within the device 10. Whilevarious force-delivery mechanisms can be used, in an exemplaryembodiment, the force-delivery element is a constant force spring 50 (asshown in FIG. 4) that is wound around and mated to a hub 38 formedwithin the driver 30, and that includes a free end that is mated to thepuller 40. In use, movement of the puller 40 will extend theforce-delivery element 50 to an expanded or unwound position. As aresult, the force-delivery element 50 will pull the driver 30 distallythereby causing the plunger to be driven into the barrel of the syringe,as will be discussed in more detail below. While the illustrated driver30 includes a hub 38 for mating to the force-delivery element 50, aperson skilled in the art will appreciate that a variety of othertechniques can be used to couple the driver 30 and the puller 40.

The puller 40 is shown in more detail in FIGS. 5A-5C. While the puller40 can have a variety of configurations, FIGS. 5A-5C illustrate asubstantially rectangular puller 40 having proximal and distal ends 40a, 40 b. The puller 40 can include rails, wheels, or some othermechanism (not shown) located on opposed sides thereof to facilitatesliding within the tracks 22 a, 22 b in the sidewalls of the frame 12(shown in FIG. 2B). The puller 40 can also include handles 44 a, 44 blocated on opposed sides thereof to facilitate movement of the puller 40within the frame 12. In an exemplary embodiment, the handles 44 a, 44 bare slidably disposed within slots 24 a, 24 b formed between the top andbottom portions 14, 16 of the frame 12. In use, a force can be appliedto the handles 44 a, 44 b such that they slide within the slots 24 a, 24b of the frame 12 thereby causing the puller 40 to slide along thetracks 22 a, 22 b in the sidewall and to move from a first position to asecond position to engage a distal portion of the frame 12 b and actuatethe force-delivery element. While the exemplary embodiment illustratesslidable movement of the puller 40 and driver 30 within the frame 12, aperson skilled in the art will appreciate that rotational or any othertype of movement can also be used to facilitate movement of the driver30 and the puller 40 within the frame 12.

As indicated above, the puller 40 is preferably configured to engage thedistal end 12 b of the frame 12. While the puller 40 can include variousfeatures to releasably mate to the frame 12 to hold the puller 40 in anactuated position, in an exemplary embodiment, the puller 40 includes alatch 46 formed therein that mates with an engagement element 18 that isformed on the distal end 16 b of the frame 12. FIG. 5C illustrates anexemplary latch 46 that includes two hook-like arms 47 a, 47 b thatextend into corresponding bores in the engagement element 18. The latch46 can be a push-push latch or a slam latch, such as those made bySouthco, or any other type of latch known in the art. In use, and upondistal movement of the puller 40, the latch 46 can be mated to theengagement element 18 to hold the puller 40 in a distal position wherebythe force-delivery element is expanded. The latch 46 and engagementelement 18 are also preferably releasable. In an exemplary embodiment,the latch 46 can be released from the engagement element 18 bydepressing the handles 44 a, 44 b on the puller 40. A person skilled inthe art will appreciate that the mating components on the frame 12 andthe puller 40 can be reversed, and the puller 40 can include anengagement element and the frame 12 can include a latch. Various othermating techniques can be used such as threads, or any other type of maleand female connector known in the art.

The device can also include features to lessen and/or prevent siphoningof fluid from the syringe when the force-delivery element 50 is in anunactuated or contracted position, and the driver and the puller 40 arelocated adjacent to one another. In one embodiment, the force-deliveryelement 50 can be positioned to push against the bottom wall of theframe 12, as shown in FIG. 6, to cause the puller 40 to be forced in anupward position, thereby generating friction between the force-deliveryelement 50 and the bottom portion 16 of frame 12 and between the puller40 and the top portion 14 of frame 12. When the force-delivery element50 is actuated, it will straighten out such that it is not in contactwith the frame 12 so that the frame 12 does not interfere with themovement of the driver 30. Additionally or alternatively, the driver 30can be configured to force the puller 40 towards the frame 12 togenerate friction between the puller 40 and the top portion of the frame12. For example, the driver 30 can include an engagement surface 52formed on a distal end 30 b thereof that contacts a correspondingengagement surface 54 formed on the proximal end 40 a of the puller 40when the driver 30 and puller 40 are positioned adjacent to one anotherwithin the frame 12. While the engagement surfaces 52, 54 can have avariety of configurations, as shown in FIGS. 4 and 5B respectively, theycan be corresponding slopes or ramped surfaces that abut against oneanother. In an exemplary embodiment, the engagement surfaces 52, 54 canhave an angle in the range of about 25-45 degrees from the direction oftravel. In use, the engagement surfaces 52, 54 can be wedged against oneanother to cause the puller 40 to be pushed upward against the topportion 14 of the frame 12 and thereby help retain the driver 30 andpuller 40 in the initial resting position. In other embodiments, therails or tracks 22 a, 22 b located in the frame 12 for slidablyreceiving the puller 40 can include bumps or detents formed thereon toprevent accidental movement of the puller 40 and the driver 30 withinthe frame 12.

FIGS. 9A-9D further illustrate the various anti-siphoning features ofthe device 10 discussed above and exemplary method for determining theforces necessary for preventing siphoning. FIG. 9A illustrates thesystem in use, showing the syringe driver 10 attached to a typical poleor stand 100. A syringe 60 is attached to the driver 10, and an IV line102 extends from the syringe 60 and includes an IV needle 104 that isinserted into the patient 106. As shown, the syringe driver 10 is at alevel higher than the insertion point of the IV needle 104. This heightdifference H creates a negative pressure within the syringe 60. In thiscondition it would be possible for the negative pressure in the syringe60 to pull the syringe plunger downward so that fluid begins to flowunintentionally, possibly causing a danger to the patient 106.

Generally, the negative pressure that occurs can be calculated using thefollowing formula:

P=D*H,

where P is the pressure, D is the fluid density, and H is the heightdifference as shown below. For water and most aqueous solutions thedensity is approximately 0.04 lb/in³. Thus, for example, a 36 inch (3foot) height difference will produce a negative pressure ofapproximately 1.4 psi. Typical syringes require about 1 to 3 psi ofpressure to overcome static friction and initiate motion of the plunger,however this varies by manufacturer and syringe size. While unwantedflow due to negative pressure will not always occur, it is likely unlessanti-siphoning features are provided. Generally, the cross-sectionalarea of the plunger for a 10 cc syringe has a maximum value of about 0.3square inches, and the force exerted by a 3 psi pressure is thereforeabout 0.9 pounds. If the anti-siphoning mechanism applies a frictionload greater than this, flow due to any height difference will beprevented.

In one embodiment, the friction load applied by the anti-siphonmechanisms can be estimated as follows, as will be discussed in moredetail below. The applied friction load is not a force itself but rathera measure of the force that must be applied to produce movement. Thefriction load can be calculated using the following formula:

F _(f) =C _(f) *F _(n),

where F_(n) is the force normal to surface, F_(f) is the appliedfriction load, and C_(f) is the coefficient of static friction, which isdependent on the specific materials employed.

As noted above, at least two anti-siphoning features have been describedfor the present invention, the first of which employs a normal forcegenerated directly by the force delivery element and the second of whichemploys an engagement surface between the puller and driver. FIG. 9Billustrates the normal force that is generated directly by the forcedelivery element 50. As shown, the force delivery element 50 ispositioned so that the extended section presses against the bottomportion 16 of the frame 12. This side load on the force delivery element50, acting normal to the bottom portion 16, can vary depending upon theexact geometry of the frame 12 and on the manufacturing process used tocreate the force delivery element 50, however the normal load can beabout one-fourth of the force delivery element tension force. By way ofnon-limiting example, if the nominal force delivery element tension isabout 3.25 pounds, the normal force will be about 0.8 pounds.

A person skilled in the art will appreciate that the coefficient offriction between the metallic force delivery element 50 and thepolymeric bottom portion 16 will depend on the properties of thematerials. For a metallic to polymeric interface, the coefficient offriction is typically about 0.2. As shown, the reaction force at theends of the force delivery element 50 is divided approximately equallybetween the puller 40 and driver 30, causing the puller 40 to be forcedagainst the top portion 14 of the frame 12 with one-half of the normalforce of the force delivery element 50. The coefficient of frictionbetween the two polymeric surfaces (that is, the puller 40 and the topportion 14 of the frame 12) will also depend on surface roughness andmaterial type. For ABS (Acrylonitrile Butadiene Styrene) type materials,the coefficient of friction is in the range of about 0.4. The overallfriction load is thus:

F _(f) =C _(f) *F _(n) +C _(f2) *F _(n)/2=0.2*.08+.04*.08/2=0.32 pounds,

where C_(f1) is the coefficient of static friction between metallic andpolymeric surfaces, and C is the coefficient of static friction betweentwo polymeric surfaces.

FIG. 9C illustrates the normal force provided by engagement surfaces 52,54 formed on the puller and driver 40, 30. As shown, the engagementsurfaces 52, 54 press the puller 40 against the top portion 12 of theframe 12 when the force delivery element 50 pulls the puller and driver40, 30 into contact with each other. As a result, the normal forcecreated can be calculated using the following formula:

F _(n) =F _(S)*tan(θ),

where θ is the contact angle. For a contact angle of 35 degrees, forexample, the friction load is then given by:

F _(f) =C _(f2) *F _(s)*tan(θ)=0.4*3.25*tan(35)=0.91 pounds.

The two friction loads, as shown in the above examples can be addedtogether for a combined total of 1.23 pounds, which is well in excess ofthe required holding force and can therefore prevent the occurrence ofany siphoning.

FIG. 7 illustrates one embodiment of a syringe 60 for use with thedevice 10. As shown, the syringe 60 is a standard syringe having aplunger 62 with a flange 63 formed on the proximal end thereof, and abarrel 64 that receives the plunger 62 and retains fluid therein. Aspreviously explained, a luer fitting is used to mate the syringe to theframe. This allows the device to work with any size syringe. While avariety of luer fittings can be used, the luer fitting 66 can include afemale fitting 70 on one end and a male fitting 72 on the opposite end.The female fitting 70 has a substantially cylindrical opening and canmate with the distal end 60 b of the syringe 60. The male fitting 72 isadapted to mate with the connecting element of the frame 12, and thushas a collar portion or barrel for receiving the protrusion 29. A fluidconduit, such as tubing, for fluid delivery can also extend from themale fitting 72. In use, the collar of the luer fitting can be placedwithin the cavity 28 of the connecting element and the underside of thecollar can be engaged by the protrusion 29 such that the luer fitting 66is securely held within the frame 12. While the luer fitting 66 can becoupled to any size syringe, in an exemplary embodiment the syringe 60has a volume in the range of about 5-60 cc, and more preferably about10-60 cc.

$F_{fA} = {\frac{L_{1}}{L_{1} - L_{2}}*C_{f\; 2}*F_{s}*{{\tan (\theta)}.}}$

At B the friction load can be calculated using the following formula:

$F_{fB} = {\frac{L_{2}}{L_{1} - L_{2}}*C_{f\; 2}*F_{s}*{{\tan (\theta)}.}}$

Thus, the total friction load is increased by

$\frac{L_{1} + L_{2}}{L_{1} - L_{2}}.$

If, for example, the puller 40 is relieved for ¼ of its length, thefriction load is increased by a factor of 1.67. A person skilled in theart will appreciate that the syringe driver of the present invention canhave a variety of other modifications to create a greater holding forceand prevent anti-siphoning.

FIG. 10 shows an exemplary embodiment of a luer fitting 66 for use withthe syringe driver of the present invention. The luer fitting 66 issimilar to a standard luer, and it includes a female fitting 70 having asocket 79 that is adapted to mate to a barrel of a syringe, and a malefitting 72 for receiving a fluid conduit, such as tubing. As shown, themale fitting 72 has a collar 69 that surrounds a nozzle 71, and a socket67 formed between the collar 69 and the nozzle 71. The socket 67 of themale fitting 72, however, is non-threaded to allow the protrusion to bereceived therein without threading the luer fitting 66 into theconnecting element. The additional benefit of the exemplary luer fitting66 is that standard luer fittings, which have threads on the socketand/or collar walls, cannot mate to the device 10. This ensures thatincorrect fluid conduits or luer fittings 66 will not be used with thedevice 10. The fluid conduit can be mated to the luer fitting 66 using avariety of techniques. For example, the fluid conduit can be secured tothe nozzle 71 of the luer fitting 66 using an adhesive, such as glue.

FIGS. 8A-8C illustrate one exemplary method for driving fluid from asyringe using the system of FIGS. 1-7. Referring first to FIG. 8A, thedriver 30 and the puller 40 can be slid to the proximal end of the frame12 a such that they are in contact with one another to create sufficientspace within the frame 12 for receiving the syringe 60. The femalefitting 70 of the luer fitting 66 can be placed on the distal end of thesyringe 60 to prepare the syringe 60 for mating with the frame 12. Thesyringe 60 can then be positioned within the frame 12 by mating the luerfitting 66 to the connecting element located on the top portion 14 ofthe frame 12. Preferably, the male fitting 72 is engaged by theprotrusion of the connecting element such that luer fitting 66 sitswithin the cavity 28 and the fluid conduit (not shown) is positionedwithin and extends outwardly from the cut-out of the protrusion. Theplunger 62 of the syringe 60, and preferably the flange 63 formedthereon, can then be engaged by the cavity 34 on the driver 30, and thebarrel 64 of the syringe 60 can be positioned within the cavity 17 ofthe frame. Where the syringe plunger is cut off or is short, aprosthetic plunger (not shown) can be mated to the shortened plunger, sothat it can be engaged by the driver 30. The prosthetic plunger can beattached to the device 10 by a flexible cord, chain, or other componentto prevent loss of the prosthetic plunger when it is not in use.

Once the syringe 60 is positioned within the frame 12, theforce-delivery element can be actuated to move from a contractedposition to an expanded position to apply force to the driver 30, andthereby cause the plunger 62 to move into the barrel 64 of the syringe60. As noted above, the puller 40 can be used to actuate theforce-delivery element. As shown in FIG. 8B, the puller 40 can be slidwithin the frame 12 from a first position where the puller 40 issubstantially adjacent to the driver 30 to a second position where thepuller 40 is positioned at the distal end 12 b of the frame 12. Thismovement can be achieved by a two-handed technique where a user canoptionally position their thumbs on the protrusions 26 a, 26 b on thedistal end of the frame 12 b and their fingers on the handles 44 a, 44 bof the puller 40 to apply a force to the handles 44 a, 44 b to therebyslide the handles 44 a, 44 b within the slots 24 a, 24 b of the frame12. Once at the distal end 12 b of the frame 12, the latch located onthe puller 40 can engage and mate to the engagement element on the frame12.

As the puller 40 moves from the first position to the second position,the force-delivery element is moved from a contracted position, where itis wound on the hub of the driver 30, to an expanded position. Once thepuller 40 is mated to the distal end of the frame 12, the force-deliveryelement is held in the expanded position, and will begin to recoilwithin the hub of the driver 30 to return to its contracted position. Asshown in FIG. 8C, the recoiling of the force-delivery element causes aforce to be applied to the driver 30 such that the driver 30 slidesalong the tracks (track 24 a is shown) in a distal direction towards thepuller 40 and the distal end 12 b of the frame 12. The driver 30 thusforces the plunger 62 into the barrel 64 of the syringe 60, therebycausing fluid to flow from the syringe 60 and into the fluid conduitextending therefrom to be delivered to the patient. Once fluid deliveryis complete and the force-delivery element returns to its contractedposition, the latch and the engagement element can be disengaged bydepressing the handles 44 a, 44 b on the puller 40. As a result, thedriver 30 and the puller 40 can be moved towards the proximal end of theframe 12 a to allow the syringe 60 to be removed and a new syringe to beadded.

In other embodiments, the syringe drivers disclosed herein can bereconditioned for reuse after at least one use. Reconditioning caninclude any combination of the steps of disassembly of the device,followed by cleaning or replacement of particular pieces, and subsequentreassembly. By way of example and in the event that the connectingelement and/or the luer fitting breaks or otherwise needs to bereplaced, it can be removed from the device and selectively replaced.Upon replacement, the device can be reassembled for subsequent use.Those skilled in the art will appreciate that reconditioning of asyringe driver device can utilize a variety of techniques fordisassembly, cleaning/replacement, and reassembly. Use of suchtechniques, and the resulting reconditioned syringe driver device, areall within the scope of the present application.

A person skilled in the art will appreciate that the present inventioncan be made of any material that is durable such that the device can bereusable as well as able to withstand being dropped from at least 1.5 monto a hard surface (such as a floor). Exemplary materials includeplastics and metals. A person skilled in the art will further appreciatefurther features and advantages of the invention based on theabove-described embodiments. Accordingly, the invention is not to belimited by what has been particularly shown and described, except asindicated by the appended claims. All publications and references citedherein are expressly incorporated herein by reference in their entirety.

1. A luer fitting for connecting a syringe barrel to a syringe driver,comprising: a proximal female end including a socket adapted to beremovably mated to a male luer fitting on the syringe barrel; and adistal end including a nozzle adapted to receive a fluid conduit, thedistal end having a non-threaded axially-oriented annular socket formedtherein for removably receiving a protrusion on the syringe driver. 2.The luer fitting of claim 1, further comprising a collar portion orbarrel formed around the nozzle in the distal end of the luer fitting.3. The luer fitting of claim 1, wherein the non-threadedaxially-oriented annular socket in the distal end of the luer fitting isformed between the collar portion or barrel and the nozzle.
 4. The luerfitting of claim 1, further comprising a fluid conduit mated to thedistal end of the luer fitting.